This invention arose from a search for a better way of steering track-laying vehicles, although the resulting discoveries also apply to many types of wheeled vehicles. Track-laying vehicles such as tractors are steered by a clutch and brake system that can unclutch the power to one track and brake one track while another track drives. Such arrangements are expensive and troublesome for many reasons, however.
For example, disconnecting power to the left track of a tractor running on level ground tends to make the tractor turn left because the driving right track outdistances the left, but doing the same thing when the tractor is running downhill tends to make it turn right because the engine holds the right track back while the left rolls free. Braking tracks to slow down tends to straighten the line of travel so drivers must guard against braking on curves. Also, the sharpest turn a track-laying vehicle can make is by braking one track while driving the other, and this stresses the braked track considerably.
In searching for a better solution for these and other problems, we have discovered a way of imposing differential rotation on axle shafts for steering both track-laying and wheeled vehicles. Our imposed differential can simultaneously drive wheels or tracks forward on one side of a vehicle and backward on the other side to allow pivot turns around a central point without overly stressing tracks or wheels. Our system can apply main propulsion drive torque to such pivot turns to accomplish them rapidly, if necessary. Our discovery also provides a no-slip differential that drives both sides of a vehicle regardless of relative traction and applies more power to the side with the greater traction.
Our invention also leads to an improvement in wheel dynamometers for testing drive axles. It allows differential rotation to be imposed realistically on axle shafts under load. Our invention also accomplishes these advances by combining inexpensive and well-known components in ways that produce improved results.